Growth and SporuZation of Tertian Malarial Parasites. 85 



Summary. 



(1) The malignant tertian parasite has heen successfully cultivated after 

 the method of Bass and Johns on twelve occasions, and the benign tertian 

 on three. 



(2) It is unnecessary to remove the leucocytes from the blood before 

 incubation. The optimum temperature wovdd appear to be about 38° C, and 

 the parasites may grow successfully at a temperature as low as 36° or 37° C. 



(3) The time required for the full development of the parasite in vitro varies, 

 but this variation is partly due to the age of the parasite at the time of 

 incubation. 



(4) The cultures of benign tertian differed from those of malignant tertian 

 in that there was no tendency to clumping of the parasites in the former, 

 either before or during sporulation. 



(5) This difference appears to us to explain in a satisfactory manner why 

 only young forms of malignant tertian are found in the peripheral blood, as 

 the clumping tendency of the larger forms causes them to be arrested iu the 

 finer capillaries of the internal organs. It also explains the tendency to 

 pernicious symptoms, such as coma, in malignant tertian malaria. All stages 

 of the benign tertian parasite are found in the peripheral blood, and there are 

 seldom pernicious symptoms, because there is no tendency to clumping. 



(6) The malignant tertian parasite {P. falciparum) is capable of producing 

 in maximum segmentation, 32 spores. On the other hand, benign tertian 

 (P. vivajc) produces, as a rule, during maximum segmentation, 16 spores ; 

 sometimes more may be produced, but the number is never 32. 



(7) The pigment in P. falciparum collects into a definite, circular, and very 

 compact mass early in the growth of the parasite. On the other hand, during 

 the growth of P. vivar the pigment remains scattered in definite granules 

 throughout the body of the parasite, till just before segmentation, when it 

 collects into a loose mass of granules in the centre of the full-grown 

 Plasmodium. 



(8) The morphology of P. falciparum and P. vivax in the human host is 

 identical with the morphology of these parasites as obtained in the cidture 

 tube. 



REFERENCES TO LITERATURE. 



Bass and Johns (1912). "The Cultivation of Malarial Plasmodia {Plasmodium vivcu; and 



Plasmodium falciparum) iu vitro," ' Journ. Exp. Med.,' vol. 16, pp. 567-579. 

 Deaderick (1910). ' Malaria.' 



Gulland, G. L., and Goodall, A. (1912). ' The Blood ; a Guide to its Examination and 

 to the Diagnosis and Treatment of its Diseases.' 



